Tetrahydrofuran

Tetrahydrofuran (THF) is an organic compound with the formula (CH₂)₄O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is mainly used as a precursor to polymers. Being polar and having a wide liquid range, THF is a versatile solvent.

Production

About 7008200000000000000♠200000 t of tetrahydrofuran are produced annually. The most widely used industrial process involves the acid-catalyzed dehydration of 1,4-butanediol. The method is similar to the production of diethyl ether from ethanol. The butanediol is derived from condensation of acetylene with formaldehyde followed by hydrogenation.Du Pont developed a process for producing THF by oxidizing n-butane to crude maleic anhydride, followed by catalytic hydrogenation. A third major industrial route entails hydroformylation of allyl alcohol followed by hydrogenation to the butanediol.

Other methods

THF can also be synthesized by catalytic hydrogenation of furan.Certain sugars can be converted to THF, although this method is not widely practiced. Furan is thus derivable from renewable resources.

Follicular B helper T cells

Follicular B helper T cells (also known as just Follicular helper T cells or T_FH), are antigen-experienced CD4⁺T cells found in the periphery within B cell follicles of secondary lymphoid organs such as lymph nodes, spleens and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5. Upon cellular interaction and cross-signaling with their cognate follicular (Fo B) B cells, T_FH cells trigger the formation and maintenance of germinal centers through the expression of CD40 ligand (CD40L) and the secretion of IL-21 and IL-4. T_FH cells also migrate into these seeded germinal centers, predominantly composed of rapidly dividing and mutating B cells. Within germinal centers, T_FH cells play a critical role in mediating the selection and survival of B cells that go on to differentiate either into special plasma cells capable of producing high affinity antibodies against foreign antigen, and memory B cells capable of quick immune re-activation in the future if ever the same antigen is re-encountered. T_FH cells are also thought to facilitate negative selection of potentially autoimmune-causing mutated B cells in the germinal center. However, the biomechanisms by which T_FH cells mediate germinal center tolerance are yet to be fully understood.

THF (disambiguation)

THF may refer to: